MultithreadEventExecutorGroup
public abstract class MultithreadEventExecutorGroup extends AbstractEventExecutorGroup {
private final EventExecutor[] children;
private final Set readonlyChildren;
private final AtomicInteger terminatedChildren = new AtomicInteger();
private final Promise> terminationFuture = new DefaultPromise(GlobalEventExecutor.INSTANCE);
private final EventExecutorChooserFactory.EventExecutorChooser chooser;
/**
* Create a new instance.
*
* @param nThreads the number of threads that will be used by this instance.
* @param threadFactory the ThreadFactory to use, or {@code null} if the default should be used.
* @param args arguments which will passed to each {@link #newChild(Executor, Object...)} call
*/
protected MultithreadEventExecutorGroup(int nThreads, ThreadFactory threadFactory, Object... args) {
this(nThreads, threadFactory == null ? null : new ThreadPerTaskExecutor(threadFactory), args);
}
/**
* Create a new instance.
*
* @param nThreads the number of threads that will be used by this instance.
* @param executor the Executor to use, or {@code null} if the default should be used.
* @param args arguments which will passed to each {@link #newChild(Executor, Object...)} call
*/
protected MultithreadEventExecutorGroup(int nThreads, Executor executor, Object... args) {
this(nThreads, executor, DefaultEventExecutorChooserFactory.INSTANCE, args);
}
/**
* Create a new instance.
*
* @param nThreads the number of threads that will be used by this instance.
* @param executor the Executor to use, or {@code null} if the default should be used.
* @param chooserFactory the {@link EventExecutorChooserFactory} to use.
* @param args arguments which will passed to each {@link #newChild(Executor, Object...)} call
*/
protected MultithreadEventExecutorGroup(int nThreads, Executor executor,
EventExecutorChooserFactory chooserFactory, Object... args) {
if (nThreads <= 0) {
throw new IllegalArgumentException(String.format("nThreads: %d (expected: > 0)", nThreads));
}
//任务执行器,每个task创建一个新的线程执行
if (executor == null) {
executor = new ThreadPerTaskExecutor(newDefaultThreadFactory());
}
//创建EventExecutor数组,长度nThreads
children = new EventExecutor[nThreads];
for (int i = 0; i < nThreads; i ++) {
boolean success = false;
try {
//循环调用子类实现
children[i] = newChild(executor, args);
success = true;
} catch (Exception e) {
// TODO: Think about if this is a good exception type
throw new IllegalStateException("failed to create a child event loop", e);
} finally {
if (!success) {
//如果失败,循环所有EventExecutor进行关闭
for (int j = 0; j < i; j ++) {
children[j].shutdownGracefully();
}
for (int j = 0; j < i; j ++) {
EventExecutor e = children[j];
try {
while (!e.isTerminated()) {
e.awaitTermination(Integer.MAX_VALUE, TimeUnit.SECONDS);
}
} catch (InterruptedException interrupted) {
// Let the caller handle the interruption.
Thread.currentThread().interrupt();
break;
}
}
}
}
}
//创建一个选择器,children是一个数组,里面每个元素就是一个EventLoop
chooser = chooserFactory.newChooser(children);
final FutureListener
其中比较一个重要的方法就是newChild,由子类实现,创建EventExecutor的实现,这个类就是一个EventLoop,简单来说就是一个队列,包含一个线程,线程死循环从队列拿出task去执行。而ExecutorGroup就是管理这一组对象。private final EventExecutor[] children;
protected abstract EventExecutor newChild(Executor executor, Object... args) throws Exception;
我们再来看一下NioEventLoopGroup的实现。创建了EioEventLoopGroup。
@Override
protected EventLoop newChild(Executor executor, Object... args) throws Exception {
return new NioEventLoop(this, executor, (SelectorProvider) args[0],
((SelectStrategyFactory) args[1]).newSelectStrategy(), (RejectedExecutionHandler) args[2]);
}
另外一个重要的方法next(),使用chooser.next方法,去在数组中选择一个NioEventLoop
//选择一个EventLoop,轮训算法。
@Override
public EventExecutor next() {
return chooser.next();
}
private static final class PowerOfTwoEventExecutorChooser implements EventExecutorChooser {
private final AtomicInteger idx = new AtomicInteger();
private final EventExecutor[] executors;
PowerOfTwoEventExecutorChooser(EventExecutor[] executors) {
this.executors = executors;
}
@Override
public EventExecutor next() {
return executors[idx.getAndIncrement() & executors.length - 1];
}
}